1. Field of the Invention
The present invention relates to a device for moving an element between two end positions and for selectively holding this element alternately in one of these end positions, the device comprising an energy buffer mechanically coupled with the element, the buffer capable of being in one of two corresponding stationary end states where the energy present therein is completely in the form of potential energy, as well as in intermediate translation states where its energy is in the form of kinetic energy that has been derived from the potential energy; a mass which is driven by the energy buffer and moved to one of two end positions which correspond with the end states of the energy buffer; locking means for each of the two end states of the energy buffer, i.e., in order to hold the element in one of its positions; and energy supply means for the energy buffer.
2. The Prior Art
Such a device is shown in U.S. Pat. No. 3,248,497. The device is used for operating a switch, the element being the movable contact of the switch or the drive for this contact.
This element consists of a rod, one end of which is fixedly coupled with the connecting portion of a fork, the teeth of which consists of flat parallel strips. The other end of the rod supports the movable contact of the switch. The fork together with the element and the contact can be moved in its longitudinal direction and can be seen partly as the above-noted mass, in combination with the element and contact.
A helical spring is positioned between a spring support, mounted on the rod, and the wall of a housing passed by the rod. The spring and the bellows and the air pressure acting upon the bellows function as the above-noted energy buffer. This helical spring, in combination with the air pressure acting upon the bellows of a vacuum switch, is dimensioned such that, when the element, i.e., the switch, the rod and fork is locked in one of the two end positions of a longitudinal movement, a force is always acting hereupon, which force in each of these extreme positions drives the contact with the same force backward to an intermediate position. Consequently, in these extreme positions an amount of potential energy is stored in the bellows with the air pressure acting thereupon or in the helical spring. As soon as the locking in one of the extreme positions is removed, this contact is driven in the other direction, while transforming potential energy in the helical spring or in the bellows and the air pressure acting thereupon into kinetic energy, which results in a movement of the fork, the rod and the contact. This movement will be in the switch on or switch out direction, depending on the prior position.
Adjacent the connecting portion of the fork a first cross pin is fixedly mounted between the parallel strips, forming the teeth of the fork. The intermediate portion of this pin passes a slot in a triangular plate, also mounted between the teeth of the fork, which plate can swing about a second cross pin, positioned adjacent the free ends of the noted teeth of the fork. The distance from the slot to the swing point, i.e., the second cross pin, may vary, so that when the swing plate is swinging, the fork and the rod connected thereto, as well as the contact, will be moved in their longitudinal direction. Hence the contact can be moved between one of its extreme positions. Therefore the switch can be switched on or switched out, respectively, by the swinging movement of the plate. The swing plate can be swung to the one position by means of an electromagnet and is held in the other swing position by means of a draw spring, as long as the electromagnet is switched off.
Upon swinging movement of the plate in order to switch on or switch out the switch, a part of the displacement energy for the contact will be supplied by the potential energy, caused by the spring force of the stored potential energy in the spring between the wall of the housing and the spring support or in the bellows and the air pressure acting thereupon, all acting upon the contact, the rod and the fork. The spring forces acting upon the switch contact and the moving mass are tuned such to one another, that the correct switch velocity will be reached and the least possible energy will be lost as collision energy. This will result in a minimum of contact deformation caused by contact collision.
Special means will be necessary to provide the contact pressure, because none of the springs, contributing to the contact movement can provide this contact pressure. Also with this special means possible contact deformation and/or contact wear can be compensated. These means consist of a lever which extends transversely to the longitudinal direction of the fork and which can swing about a point at one of its ends. The lever extends between the free ends of the parallel teeth of the fork and here supports the second cross pin, about which the swing plate can swing. The two free ends of this second cross pin traverse longitudinal slots in the free ends of the said fork teeth. A pressure spring acts on the free end of the lever, pushing upwards the lever and therewith the swing plate, the fork via the first cross pin and also the contact. This provides for the necessary contact pressure and compensates contact wear and contact deformation.
As a matter of course these last noted means should be made inoperable as soon as the switch is switched off. Thereto the free end of the lever cooperates with the magnetic means which secure the lever when reaching the lowest position upon switching off, in which the lever is pressed downwards by the fork through the second cross pin and by the upper edges of these transverse slots.